Refrigerating apparatus



Aug. 11 1930. R, EHR W 2,050,650

'REFRIGERAT ING APPARATUS Filed May 30, 1933 2 SheetsSheet l Aug. 11, 1936. JKRFEHR REFRIGERATING APPARATUS Filed May 30, 1933 2 Sheets-Sheet 2 Patented Aug. 11, 1936 2,050,650 REFRIGERATING APPARATUS John Ralph Fehr, Dayton, Ohio, assignor, by mesne assignments, to General Motors Corporation, a corporation of Delaware Application May 30, 1933, Serial No. 673,720

17 Claims.

This invention relates to refrigerating apparatus and more particularly to mechanisms for defrosting or removing the frost from cooling units of refrigerating apparatus.

In the use of household refrigerator cabinets, it is customary to maintain the temperatures of the cooling unit below freezing to provide ice cubes and in some instances frozen comestibles as well as to cool the air within the refrigerator cabinet. .The operation of the evaporator at a temperature below freezing, causes frost to collect upon the air cooling surfaces of the cooling unit. This frost acts as an insulator between the cooling unit and the ambient air and reduces the efficiency of the heat transfer between the air and the cooling unit.

This frost must be removed from the cooling unit or coil periodically and in the past this has been accomplished by merely discontinuing the operation of the refrigerating apparatus. While this method of removing frost is quite simple, it frequently happens that the user forgets to restore the apparatus, resulting in a prolonged absence of refrigeration.

The objects of my invention are to eliminate the objectionable features of former methods of defrosting by the provision of defrosting mechanism which will automatically restore the refrigerating apparatus to its normal operation after the defrosting is completed; and particularly a mechanism which may be operated as a fully automatic mechanism or a semi-automatic mechanism for defrosting.

It is a further object of my invention to incorporate such a defrosting mechanism into and with the temperature regulating mechanism so that all may be operated and controlled by the same operating member and so that the defrosting mechanisms are rendered ineffective when the temperature regulator is moved to provide colder than normal cooling unit temperatures.

It is another object of my invention to control all of these defrosting devices as well as the temperature regulator by a single manual control means and to so construct this manual control means so that only one of these devices will be eflective at a time.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred form of the present invention is clearly shown.

In the drawings: g Fig. 1 is a view of a refrigerating apparatus partly diagrammatic embodying my invention;

Fig. 2 is a top view of the control portion or means in Fig. 1;

Fig. 3 is an enlarged end view of the control means shown in Fig. 1; and

- Fig. 4 is a sectional view along the line 4--4 5 of Fig. 3.

Referring to the drawingsand more particularly to Fig. 1 there is shown a refrigerating system including a compressor 20 for compressing the refrigerant and forwarding the compressed 10 refrigerant to a condenser 2| where the refrigerant is liquefied and collected in a receiver 22. From the receiver, the liquid refrigerant is forwarded through the supply conduit 23 to a float controlled flooded evaporator 24 which is located 15 within the food compartment 25 of a refrigerator cabinet 26. The cooling unit 24 absorbs heat from the air within the interior of the food compartment 25 causing the evaporation of liquid refrigerant, which evaporated refrigerant is re- 20 turned to the compressor through the return conduit 21. The compressor 20 is driven by the electric motor 28 through suitable pulley and belt means 29. The electric motor 28 is provided with electrical supply conductors 30 and 3|. I

The temperature of the flooded type evaporating means 24 is controlled by a control means, generally'designated by the reference character 32, which is in series with the electrical supply conductor 3| so as to control the operation of the electric motor. The control means 32 is connected to the return conduit 21 by a suitable tube 33 so that the control means operates according to the pressure within the evaporator 24, which pressure is proportional to the temperature of the evaporator. The control means 32 therefore controls the starting and stopping of the compressor according to the temperature and pressure of the evaporator 24. h 40 Referring now particularly to the control means 32, there is provided a platform 35 upon which is mounted a metal bellows 36, the interior of which is connected to the tube 33. Above the bellows 36 is a lever 31 which is connected tothe bellows 36 by a bellows follower 38. Surrounding the bellows 36 is a sort of a cage 39 which is supported by the platform 36 and which is provided with a bearing 40 which supports a pivot pin 4| for pivotally supporting the end of the lever 31. The opposite end of the lever 31 is connected to a snap acting switch mechanism. This snap acting switch mechanism comprises a lever 42 which is pivotally mounted upon a pin 43 which is fixed to the main lever 31. This secondary lever 42 is made in two parts, one on either side of the lever 31 and these parts are connected together by suitadapted to co-act with a spring pressed cam roller 46 mounted upon the upper end of a spring pressed lever 41 and pivoted at its lower end upon a pin 48 which has its end mounted in an inverted U-shaped standard 49. The lever 41 is urged in a counter-clockwise direction about its pivot pin 48 by a spring 12 so that the roller 46 is resiliently held against the cam 45. The standard 49 rests upon the platform member 35 and at its upper end carries a differential adjustment means 50 which contains a movable plunger 5| which is spring pressed against a shoulder within the differential adjustment means. The lower end of this plunger 5| is adapted to engage the upper portion of the extreme end of the main lever 31 when this main lever end is in its upper position. However, when the main lever is moved to its lower position, the shoulder within the differential adjustment means prevents the plunger from continuing to follow the main lever in its downward movement. In this way the lever 31 is only affected by the differential adjustment means at its upper limit to provide a differential adjustment.

A range adjustment means is also provided for the main lever 31. This range adjustment means comprises a vertical rod 55 which has its upper and lower ends threaded and which is fastened at its upper end by means of a pin 56 to the main lever 31. The rod 55 of the range adjustment means passes through the platform 35 and is surrounded by a large spring 51 above the platform and a small spring 58 below the platform. The tension of the spring 51 is controlled by a pair of nuts 59. one serving as an adjusting nut, and the other as a lock nut. Likewise, the tension of the spring 58 is controlled by a pair of nuts 60, one serving as an adjustingnut and the other as a lock nut. By means of the tensioning of the springs 51 and 58, the pressure required within the bellows 36 in order to move the lever 31 in one direction or the other is controlled.

The end of the secondary lever 42 opposite the cam 45 is connected by a long pin 64 to an insulating link 65 which in turn is connected by means of a pin to a movable contact member 66. This movable contact member 66 is adapted to cooperate with a stationary contact 61 mounted upon the platform 35. In order to guide the movement of the movable contact 66 this movable contact member is connected by means of copper strips 68 which are pivoted at their opposite end to an insulating member 69 which is mounted beneath an aperture 10 in the platform 35. One portion of the electrical supply conductor 31 is connected to'one of the copper strips 68 while the other portion is connected to the stationary contact 61.

By means of this mechanism, as the temperature and pressure within the cooling unit 24 rises, the bellows 36 expands under control of the springs 51 and 58 so that the free end of the main lever 31 moves upwardly and contacts the lower end of the plunger 5| forming a part of.

the differential adjustment means. As the main lever 31 continues its upward movement, the

plunger 5| is moved upwardly against the tension of its own spring member and finally the cam 45 is moved upwardly from a position beneath the cam roller 46 to a position above the roller so that the secondary lever 42 is caused to turn counterclockwise about its pivot pin 43 to move the movable contact 66 into contact with the stationary contact 61. This closes the circuit to the electric motor 28 and starts the operation of the compressor 20. The operation of the compressor 28 removes the vapor from the cooling unit 24 and condenses this vapor in the condenser 2|. This in turn causes the pressure within the return conduit 21 to be lowered and this lowering of the compressor tends to contract the bellows 36 against the tension of the range adjusting springs 5! and 58. The main lever 31 moves downwardly because of the contraction of the bellows 36 and causes the cam 45 to move from the position above the cam roller 56 to a position below the cam roller 46. This cam roller 46, is, of course, pressed against the surface of the cam 45 by the spring 12 which urges the cam roller lever 41 in the counterclockwise direction about the pivot pin 48. The urging of the cam roller against the upper face of the cam 45 causes the lever 42 to move in a clockwise direction about its pivot pin 43 to open the switch contacts 66 and 61. e

upon the end of a shaft 18 rotatably mounted in the vertical portion of the L-shaped bracket 15. The shaft 18 extends a considerable distance back of the vertical portion of the L-shaped bracket 15 and has a temperature regulating spring 19 having a portion coiled thereabout. The forward end of this coil portion extends into -a slot 8| which extends through the greater portion of the 'shaft 78. Extending from the other-end of the coil portion of the spring is a straight portion which is adapted to engage, when moved into position, an extension of the pivot pin 43. When this straight end portion of the temperature regulating spring is moved into contact with the pivot pin 43 it assists the bellows in moving the switch to closed circuit position and thus causes the electric motor to operate for longer periods of time so as to reduce the average temperature of the evaporator 24 below normal. The handle '11 is provided with an engaging pin beneath its knob which is adapted to engage apertures 82 extending around the outer portion of the dial 16. Some of these apertures are designated 1, 2, 3, 4, and 5 which designate the various temperature regulating positions. When the handle 11 is moved to number 1 position, the free end of the temperature regulating spring 19 engages the pivot pin 43 to apply pressure thereon in order to urge it upwardly with a certain tension. When the handle 11 is moved to number 2 position, an increased tension or pressure is applied to the pin 43, while when the handle is moved to position 3, 4, and 5, an increased pressure or tension upon the pin 43 is made in each case. vice the temperature of the cooling unit 24 may be lowered at any time below the normal average temperature in five different degrees, any of which may be selected.

S Stated in the beginning of the specification,

Thus, by this de- I the evaporator 24 is normally maintained below freezing temperatures. This causes frost to accumulate upon the surface of the evaporator and this frost acts as a sort of an insulator. By acting as an insulator, the efficiency of heat transfer is reduced between the air in the cabinet and the liquid refrigerant within the cooling unit 24. This also lowers the entire operating efficiency of the refrigerating system. In order to maintain a reasonable operating eificiency it is therefore necessary to remove this frost from the cooling unit whenever it builds up to a substantial amount. The most convenient way of doing this is to permitthe temperature of the evaporator to rise above the freezing temperature and thus cause the frost to melt from the cooling unit. However, this is not without objectionable features. evaporator of the cooling unit 24 above freezing temperatures causes the temperature to be increased within the cooling compartment 25 and thus increases the danger of food spoilage; hence when there is a large amount of food within the cabinet which might be damaged by the increase in temperature, it-is undesirable to have any defrosting at such a time. For this reason, it is often desirable to wait until the food supply within the refrigerator is low before. defrosting is attempted. The increase of the temperature of the evaporator above the freezing point also delays or prevents the freezing of ice cubes, desserts, and other comestibles within the evaporator or cooling unit 24. This increase in temperature may also cause the melting of any ice cubes which maybe in the evaporator during a defrosting period. Some of the other objections to this defrosting have been that the housewife does not defrost her cooling unit regularly enough or often enough and also that sometimes she begins a defrosting period and then forgets to terminate this defrosting period at the proper time when the cooling unit has been completely defrosted. Y

In the past it has been customary to defrost the cooling unit or evaporator by the shutting off of the refrigerating apparatus for a period of time suflicient to raise the temperature of the evaporator above freezing for a long enough time to cause the frost to completely melt from the cooling unit. Thereafter it was necessary to again restart the apparatus. While this arrangement was fairly satisfactory in that it permitted the defrostingof the refrigerator at any time desired by the housewife and for any period desired by her, it was found that this defrosting was not performed often enough or regularly enough and that the defrosting periods were often made too long and the food compartment denied refrigeration for too great a time. In order to overcome these difficulties, I provide automatic means for performing this defrosting 'which will insure that the apparatus will be restored at the proper time. In one type of such automatic means, the defrosting period is manually initiated, that is, the housewife is required to set the defrosting mechanism whenever she desires a defrosting period to occur. but mech- I anism is provided for terminating such a defrost- The increase of the temperature of the At other times these devices are objectionable. For instance, when there is provided a completely automatic defrosting device which provides periodic defrosting cycles automatically, a defrosting cycle I may occur when it is desired to freeze ice cubes or when there is a large amount of food within the refrigerator cabinet which is likely to be spoiled by such defrosting. With the other type of automatic defrosting, which is sometimes called semi-automatic, defrosting may not be performed sufficiently often and the length of defrosting period may not be sufficient if defrosting has not been attended to for a great length of time. Thus, it will be seen that there are objectionable features to each type of defrosting but there also seems to be a'place for each of these types of defrosting.

I therefore provide in my control means a provision for each of these types of defrosting means, and, further, so combine these defrosting means with the temperature regulator so that all may be controlled by the handle and further correlate these devices by means of a regulating cam so that only one will be effective at a time. Thus when the handle 1'! is in any one of the cold control positions, no defrosting will occur. When the regulating handle H is in full automatic de-. frosting position, only the periodic automatic defrosting cycles will occur. When the regulating handle 11 is in semi-automatic position, only the semi-automatic defrosting period will occur. While, if the handle 11 is moved to full defrost or off position, the operation of the refrigerating appara us will be stopped until such time as the regulating handle ii is moved to one of the other positions.

In order to provide a means for performing a fully manualdefrost, that is, by shutting off the refrigerating apparatus, I provide a sheet metal arm 90 which is keyed to the regulating shaft 18. This arm is substantially inalignnient with the regulating handle 11 and when the regulating handle 'I'l is moved clockwise to the off position, the end of this arm 90 engages the projecting end of the pin 64 so as to forcibly move the switch contact 66 to open position and to hold it there as long as the regulating handle Tl remains in this position. This arm 90 therefore serves to lock the switch in open position.

In order to provide means periodically defrosting the cooling unit, I provide a ratchet wheel slidably and rotatably mounted upon the pivot pin 43. This ratchet wheel is, of course, moved up and down by the movements of the main lever 37. Positioned in the path of movement of the ratchet wheel I00 is a spring pressed pawl [0| which is p'voted upon the pin 48 and which is urged against the stop pin I02 by a spring I03. Therefore when the ratchet-wheel Hill is moved downwardly by the main lever 31 it will engage the pawl IM and be rotated a distance of one tooth. This rotation of the ratchet wheel M0 is controlled by an aligning detent spring 104 which res liently engages the teeth of the ratchet wheel. This spring which is in the form of a leaf spring is riveted to the main lever 31.

The ratchet wheel I00 carries a pin I05 near its periphery, which pin projects from opposite sides of the ratchet wheel.

about the pin 43 just as is the ratchet wheel )0. In order to periodically increase the temperature of the cooling unit automatically, I cause this pin I85 to periodically engage a prong I 06 which forms a part of the forked end of an arm I01 This pin I05, is, of course, moved step by step or tooth by tooth,

which is pivoted upon the pin 4| which also serves as a pivot pin for the main lever 31. This arm I 01 is pulled downwardly by a tension spring I08 which is hooked at its lower end to an eye screw I09 threaded into the platforms 35 and provided with a lock nut H0. The upper end of the spring I08 is hooked on to an eye screw I I I which passes through a passage I I2 provided in the arm Resting on the upper face of the arm IN is an adjusting nut H3 which is threaded upon the eye screw I II and is provided with a lock nut II4. In order to prevent the spring I08 from pulling the arm downwardly too far and to prevent it from coming into engagement with the teeth of the ratchet wheel I00, there is a stop I05 upon the cage 39 of the bellows which engages the bottom of the arm I01 to limit its downward movement.

As stated before, the ratchet wheel I00 is slidably and rotatably mounted upon the pivot pin 43. In order to control the lateral movement of the ratchet wheel I00, there is provided a fork I20, the prongs of which are turned inwardly to engage the sides of the ratchet wheel. These prongs remain between the center of the ratchet wheel and the path of movement of the pin I 05 so that there is no interference between the prongs of the fork I20 and the pin I05. The fork I20 is pivoted at its lower end to an ear I2I which is turned out from the inverted U-shaped standard 49. This fork is also connected to a slide bar I22 provided with a forked projection I23 extending upwardly at an angle of about 45. The movement of the slide bar I22 is controlled by the pin I24 mounted in the ear I25 extending from the standard 49. This pin I24 extends into a slotted aperture I25 formed in the slide bar I 22. The forked end of the projection I23 engages a regulating cam I28 mounted upon the end of the regulating shaft I8. This regulating cam is in the form of a disc whose periphery extends into the notch which forms the forked end of the projection I23. The periphery of this cam I28 is warped or bent laterally toward the dial "I6 to form a nose I29. When the cam I28 is rotated by the handle TI the nose enters into the notch formed in the end of the projection I23 and moves the slide I22 toward the dial I6 to pivot the fork I20 counterclockwise in order to move the ratchet wheel toward the dial I6. By moving the ratchet wheel towards the dial 16, the pin I05 is caused to move directly beneath the projecting prong I06 at the end of the arm I01 in a generally elliptical path. Should this pin I05 and the prong I06 be in exact alignment when this shifting of the ratchet wheel is made, the pin I05 will cam the prong I06 and the arm I01 upwardly by reason of the inclined surface I03 which is provided on the inner side of the prong I06. Thus, the prong will be lifted on top of the pin I 05.

When the ratchet wheel is in this position, it is rotated as usual step by step, that is, tooth by tooth, by the pawl IOI. It also reciprocates as usual w th the main lever arm 31. This indexing takes place when the lever 31 is moved to its lower position and once every revolution of the ratchet wheel I00, the pin I 05 is indexed to a 7 This increase in burden is caused for the reason that the pin I05 is required to lift the arm I01 against the tension of the spring I08. This increase in pressure required in the bellows to cause the switch to move to closed circuit position delays the starting of the refrigerating apparatus for the next running period and thus causes the temperature of the evaporator to rise above the freezing point. The tension of the spring I08 is so adjusted by the nut II3 that the pressure required to close the switch at this time is one which corresponds to a temperature with in the evaporator of several degrees above freezing, for example, about 34 to 36 F.

This mechanism provides a periodic defrosting cycle each time the pin is moved into position beneath the prong I05 or, in other words, once every revolution of the ratchet wheel I00. This occurs entirely automatically so long as the handle 'I'I remains in full automatic position. However, as soon as the handle I1 is moved to one of the other positions on the dial the regulating cam I28 moves the ratchet wheel and the pin I05 away from the prong I06.

In order to provide the other form of automatic defrost, which is sometimes called semiautomatic defrosting, the ratchet wheel is moved in the opposite direction from its central position (shown in Fig. 3). When in this position the opposite end of the pin I05 is caused to en gage the other prong I35 which forms the other part of the forked end of the arm I07. This other prong has a somewhat more complex structure than the prong I06. This prong I35 has a cam or inclined surface I36 on its inner face which when engaged by the end of the pin I05 in its lateral movement when in alignment therewith causes the lifting of the arm I01. Adjacent this inclined surface I36 and directly opposite .the prong I06 there is a shoulder I3'I which forms a resting place for the pin I05. At the side of this shoulderthere is provided a vertical circuit I38 which acts as a guide and a stop to limit the movement of the pin and the ratchet wheel away from the dial I6. It is desired that when in this position there will be provided a plurality of defrosting cycles, that is, cycles in which during a portion of the time, the temperature of the cooling unit will be raised about the freezing point and after the termination of a predetermined number of these defrosting cycles that the periods be restored to normal operation. In order to do this, another cam surface I39 is provided at the rear of the guiding surface I 38. This cam surface I 39 is adapted when the ratchet wheel is indexed a predetermined number of times to move the ratchet wheel to its central position. When moving the ratchet wheel to its central or neutral position, the fork I20 is also moved thereby moving the slide bar I22 and the projecting arm I forming part of the slide bar I22 acts against the semi-automatic defrosting nose I4I upon the periphery of the cam I28 in order to cause the cam to be rotated and also the handle I1 to neutral position designated by N. In the semi-automatic position, there is no aperture provided to detain the regulating handle 'I'I in that position but merely a slight depression which may be overcome by the cam surface I39 upon the prong I which moves the ratchet wheel to neutral position. When the regulating handle is thus moved to neutral position the switch means is again set for operation without any defrosting or colder temperature regulation until the handle 11 is reset.

It will thus be seen that I have provided a refrigerating apparatus with a control means providing for suitable temperature regulation for freezing purposes, as well as three different defrosting mechanisms, each of which is individually controlled by a single regulating handle which also serves as an indicator and this handle, together with the cam I28 so correlates these devices so that only one is effective at a time.

While the form of embodiment of the invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. Refrigerating apparatusincluding a refrigerant liquefying means and a refrigerant evaporating means, means for cyclically controlling the apparatus for maintaining the evaporating means at a normal average temperature, means responsive to the cyclical operation of the apparatus for automatically, at predetermined intervals, increasing the average temperature of the evaporating means above the normal average temperature for providing periodic defrosting cycles, manually initiated means operable at will for providing defrosting cycles, said last mentioned means including automatic means for restoring the apparatus to the normal control of said control means.

2. Refrigerating apparatus including a refrigerant liquefying means and a refrigerant evaporatingmeans, means for controlling the apparatus for maintaining the evaporating means at a normal average temperature, means for automatically, at predetermined intervals, increasing the average temperature of the evaporating means above the normal average temperature for providing periodic defrosting cycles, manually initiated means operable at will for providing defrosting cycles, and means operated by the change in temperature in the apparatus during a defrosting cycle for terminating a defrosting cycle.

3. Refrigerating apparatus including a refrigerant liquefying means and a refrigerant evaporating means, means for cyclically controlling the apparatus for maintaining the evaporating means at a normal average temperature, means for automatically, at predetermined intervals, increasing the average temperature of the evaporating means above the normal average temperature for rating means above the normal average tempera- Y ture for providing periodic defrosting cycles,

-manually initiated means operable at will for temporarily increasing the temperature of the evaporating means for providing a plurality of defrosting cycles and thereafter automatically returning the apparatus to normal operation, said manually initiated means rendering said periodic means inoperative for succeeding cycles.

5. Refrigerating apparatus including a refrigerant liquefying means and a refrigerant evaporating means, means for controlling the apparatus for maintaining the evaporating means at a normal average temperature, automatic means for periodically increasing the average temperature of the evaporating means above the normal average temperature for providing periodic defrosting cycles, manually initiated means operable at will for temporarily increasing the temperature of the evaporating means for providing defrosting cycles and thereafter automatically returning the apparatus to normal operation, and selectively operable common means for selectively controlling the periodic means and said manually initiated means. 6. Refrigerating apparatus including a refrigerant liquefying means and a refrigerant evaporating means, means for controlling the apparatus for maintaining the evaporating means at a normal average temperature, automatic means for periodically increasing the average temperature of the evaporating means above the normal average temperature for providing periodic defrosting cycles, manually initiated means operable at will for temporarily increasing the temperature of the evaporating means for providing defrosting cycles and thereafter automatically returning the apparatus to normal operation, and common selective means for controlling the periodic. means and the means operable at will so that only one will be effective at a time.

'7. Refrigerating aparatus including a refrigerant liquefying means and a refrigerant evaporating means, means for controlling the apparatus for maintaining the evaporating means at a normal average temperature, automatic means for periodically increasing the average temperature of the evaporating means above the normal average temperature for providing periodic defrosting, a first means operable at will for temporarily lowering the temperature of the evaporating means below the normal average temperature for freezing purposes, a second means operable at will for providing defrosting cycles and thereafter automatically returning the ap paratus to normal operation, and common means for controlling the first and the second means operable at will.

8. Refrigerating apparatus including a refrigerant liquefying means and a refrigerant evaporating means, means for controlling the apparatus for maintaining the evaporating means at a normal average temperature, automatic means for periodically increasing the average temperature of the evaporating means above the normal average temperature for providing periodic defrosting, a first means operable at will for temporarily lowering the temperature of the evaporating means below the normal average temperature for freezingpurposes, a second means operable at will for providing defrosting cycles and thereafter automatically returning the apparatus to normal operation, and common means for controlling the periodic means and the first and second means operable at will.

9. Refrigerating apparatus including a refrigerant liquefying means and a refrigerant evaporating means, means for controlling the apparatus for maintaining the evaporating means at a normal average temperature, automatic means for periodically increasing the average temperature of the evaporating means above the normal average temperature for providing periodic defrosting, a first means operable at will for temporarily lowering the temperature of the evaporating means below the normal average temperature for freezing purposes, a second means operable at will for providing defrosting cycles and thereafter automatically returning the apparatus to normal operation, and common means for controlling the first and the second means operable at will so that only one will be'effective at a time.

10. Refrigerating apparatus including a refrigerant liquefying means and a refrigerant evaporating means, means for controlling the apparatus for maintaining the evaporating means at a normal average temperature, automatic means for periodically increasing the average temperature of the evaporating means above the normal average temperature for providing periodic defrosting, a first means operable at will for temporarily lowering the temperature of the evaporating means below the normal average temperature for freezing purposes, a second means operable at will for providing defrosting cycles and thereafter automatically returning the apparatus to normal operation, and common means for controlling the periodic means and the first and second means operable at will so that only one will be effective at a time.

11. Refrigerating apparatus including a .refrigerant liquefying means and a refrigerant evaporating means, means for controlling the apparatus for normally maintaining the evaporating means at a normal average temperature, a first means operable at will for temporarily increasing the'temperature of the evaporating means to provide defrosting cycles and thereafter automatically returning the apparatus to normal operation, a second means operable at will for shutting off the apparatus, and selective common means for selectively controlling the first means and the second means.

12. Refrigerating apparatus including a refrigerant liquefying means and a refrigerant evaporating means, means 'for controlling the apparatus for maintaining the evaporating means at a normal average temperature, a first means operable at will for temporarily increasing the temperature of the evaporating means to provide defrosting cycles and thereafter automatically returning the apparatus to normal operation, a second mass operable at will for shutting off the apparatus, a third means operable at will for temporarily lowering the temperature of the evaporating means for freezing purposes, and common means for controlling the first means, the second means, and the third means.

13. Refrigerating apparatus including a refrigerant evaporating means and a refrigerant liquefying means, control means for controlling the liquefying means to maintain a normal av- .erage temperature of the evaporating means by intermittently operating the liquefying means to provide cycles composed of an operating period and an idle period so that the temperature of the evaporating means is lowered to a predetermined normal low temperature limit during one the high temperature limit above the freezing point for each successive cycle for a predetermined number of cycles for defrosting purposes and thereafter automatically returning the refrigerating apparatus including the control means to normal operation.

14. Refrigerating apparatus including a refrigerant evaporating means and a refrigerant liquefying means control means for controlling the liquefying means to maintain a normal average temperature of the cooling unit by intermittently operating the liquefying means to provide cycles composed of an operating period and an idle pe riod so that the temperature of the evaporating means is lowered to a predetermined normal low temperature limit during one portion of the cycle and raised to a normal predetermined high temperature limit during another portion of the cycle, means operable at will for altering the operation of the control means to raise the average temperature of the evaporating means for a predetermined number of successive cycles for defrosting purposes and thereafter returning the refrigerating apparatus including the control means to normal operation.

15. Refrigerating apparatus including a refrigerant liquefying means and a refrigerant evaporating means, cyclical control means for starting and stopping the refrigerant liquefying means for maintaining said evaporating means at freezing temperatures at which frost collects O thereon, and manually initiated defrosting means operable at will for temporarily increasing the temperature of the evaporating means above ice freezing temperature for a plurality of successive cycles to'melt frost from the evaporating means and thereafter automatically returning the apparating to normal operation.

16, Refrigerating apparatus including refrigerant liquefying means and a refrigerant evaporatapparatus to normal operation, said manually initiated means including means for rendering the periodic means inoperative for succeeding cycles.

17. Refrigerating apparatus including a refrigerant liquefying means and a refrigerant evaporating means, pressure operated means for controlling the apparatus for normally maintaining the evaporating means at a normal average temperature, an abutment means, an engaging means carried by said pressure operated means, means for periodically bringing said engaging means into alignment with the abutment means to periodically vary the temperature of the evaporating means, and means for holding said engaging means out of alignment and preventing the effective operation of the periodic means.

JOHN RALPH FEI-IR. 

